Wednesday, January 16, 2013

Settled science update: Black carbon "may be trapping heat at almost three times the previously estimated rate"; planet-healing, black-carbon-spewing diesel engines may not actually be as planet-healing as advertised

The tiny black particles released into the atmosphere by burning fuels are far more powerful agents of global warming than had previously been estimated, some of the world’s most prominent atmospheric scientists reported in a study issued on Tuesday....The new estimate of black carbon’s heat-trapping power is about double the one made in the last major report by the United Nations’ Intergovernmental Panel on Climate Change, in 2007. And the researchers said that if indirect warming effects of the particles are factored in, they may be trapping heat at almost three times the previously estimated rate....Although some scientists have long believed that black carbon is a major force in climate change, the vast majority of previous mathematical models had predicted that the particles had only a modest impact. That view should now change, said Mark Z. Jacobson, an atmospheric scientist at Stanford University and one of the study’s authors, calling the old models “overly simplistic.” He said that many of his co-authors had previously hewed to the lower estimates....On another front, a greater emphasis on black carbon as a warming agent could affect elements of climate policies in many countries. Most notably, to meet national fuel efficiency standards, many carmakers are making more diesel cars because they get better gas mileage and produce less carbon dioxide.

But diesel engines also produce relatively heavy emissions of black carbon, Dr. Jacobson said, which partly cancels out the benefit.